1. Field of the Invention
The present invention relates generally to an apparatus and process for testing airflow through a turbine vane or nozzle, and more specifically to simulating the engine airflow conditions in which to test the vane.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as an industrial gas turbine engine (IGT), the turbine airfoils, such as rotor blades (also referred to as a bucket) and stator vanes (also referred to as a nozzle), are provided with internal cooling air passages and film cooling holes to provide cooling of the airfoil while exposed to the extremely high temperatures of the gas flow during engine operation. When a turbine vane, for example, is designed, it must be tested to determine if the cooling passages and film holes are sized properly in order to prevent insufficient or excessive cooling. Excessive cooling would include passing too much cooling air through the passages or film holes in which some of the cooling air is not effectively utilized. Usage of too much cooling air reduces the efficiency of the engine which leads to higher operating costs. Insufficient usage of cooling air leads to component overheating and premature replacement, and also leading to higher operating costs.
Testing the airfoil within an actual engine during real engine operation is a very expensive and time consuming way to test the part. The engine must be shut down and taken apart in order to remove the part for inspection. Test rigs have also been proposed in which the part is placed on the test rig and pressurized cooling air is passed through the part to check for airflow through individual film holes. This process has been used for small airfoils, but is not known for larger airfoils in which higher volumes of airflow is required to simulate the actual conditions for the larger airfoils.
In some engines, some of the turbine vanes are sectioned internally to provide for different levels of cooling air pressure to minimize airflow usage. The pressure side of the vane will be exposed to a higher hot gas flow pressure than would the suction side of the vane. Therefore, different cooling air flow passages are formed within the vane in which one passage would supply the pressurized cooling air to the pressure side passages while another would supply the pressurized air to the suction side passages. Under this method, the suction side can be supplied with lower pressurized cooling air without the need of bleeding off higher pressure air used for the pressure side cooling passages and reducing the pressure accordingly.
In the testing of larger airfoils such as stator vanes, pressurized cooling air is applied to one small section of the airfoil for testing and not to the entire airfoil due to the lack of high pressures and high volumes of airflow required.